Filtration unit

ABSTRACT

A disposable filtration unit for use with a specimen tube, including a hollow cylindrical filter column formed with a cap depending from the bottom of the column and dimensioned to fit the mouth of the specimen tube, the bottom of the column being formed with a depending discharge tip spaced axially centrally of the cap. The bottom of the filter column is formed with flat marginal portions and filter material is utilized in a form including flat sheet portions supported flush on the marginal filter column portions. The sample tube is formed with an exterior annular ridge spaced from its mouth and the cap is sized so as to engage the ridge to thereby space the bottom of the filter column from the mouth. One or more vent openings are defined in the cap between the sample tube mouth and the bottom of the filter column.

United States Patent 3,010,583 ll/l96l Kenyon 2 10/406 Primary Examiner-J. L. Decesare Attorney-Nilsson, Robbins, Wills 8c Berliner ABS'IRACT: A disposable filtration unit for use with a specimen tube, including a hollow cylindrical filter column formed with a cap depending from the bottom of the column and dimensioned to fit the mouth of the specimen tube, the bottom of the column being formed with a depending discharge tip spaced axially centrally of the cap. The bottom of the filter column is formed with flat marginal portions and filter material is utilized in a form including flat sheet portions supported flush on the marginal filter column portions. The sample tube is formed with an exterior annular ridge spaced from its mouth and the cap is sized so as to engage the ridge to thereby space the bottom of the filter column from the mouth. One or more vent openings are defined in the cap between the sample tube mouth and the bottom of the filter column.

YPATENTEUSEP28I97I 3, 0 ,735

Aw, I. I. I. I

INVENTOR. JOHNSON Al. 5. WONG c/lmm 8 CW FILTRATION UNIT FIELD OF THE INVENTION The field of art to which the invention pertains includes the field of filtration.

BACKGROUND AND SUMMARY OF THE INVENTION In the analysis of biological materials, such as blood serum, it is often important to remove particulate materials in the serum prior to analysis. This is particularly true when automatic analytical devices are used which often involve the utilization of capillary openings which could be clogged by particulate matter in unfiltered serum. Filtration methods which involve the handling of a large number of samples at one time typically utilize racks of filter columns which are supported over rackes of specimen tubes carefully disposed in alignment. Blood samples which are numbered in sequence with the numbering of the specimen tubes are poured through the filter columns for gravity discharge into appropriate specimen tubes. A disadvantage of this arrangement is that the racks can be misaligned resulting in a distribution of the blood serum into wrong specimen tubes. As one means of preventing this, the prior art has utilized three separate labels with the same number, one label on the original tube containing the patients blood as obtained from the doctor, another label on the specimen tube for subsequent identification and a label bearing the same number on the racked filter column. At any point in time, the number on the filter column must match the number on the specimen tube and constant surveillance is required.

The present invention provides a filtration unit which does not suffer the foregoing drawbacks in that the filter column of the present invention is designed so as to stay with the specimen tube until discarded. Accordingly, once the blood sample has been poured into the filter column, there need be no further concern with respect to misalignment. In particular, a disposable filtration unit is provided herein comprising a filter column in the form of a hollow body having an open top end and a discharge bottom end, means for supporting filter material internally of the body, and means integral with the bottom end for removably fitting the filtration unit to the mouth of a receptacle such as a specimen tube. The filter column has a sidewall with a vertical dimension as least as great as its longest horizontal dimension and may be cylindrical. In terms of specific construction, the bottom end of the filter column is formed with flat marginal portions and has a discharge tip depending centrally therefrom. The filter material is in a form including flat sheet portions supported flush on the marginal portion of the bottom end. The filter material can be constructed from a circular disc of filter paper pushed to the bottom of the filter column; accordingly the filter material has only a minor extent along the vertical dimension of the filter column.

It is contemplated that the filtration unit would be utilized with a specimen tube having a cylindrical top portion defining a mouth. Therefore, accordingly, the bottom of the filter column is formed integrally with a cylindrical cap for the specimen tube and the discharge tip is spaced axially central of the cap. The specimen tube has an exterior annular ridge spaced from its mouth and the cap slide-fits over the mouth to engage the ridge to thereby space the bottom of the filter column from the specimen tube mouth. The cap defines one or more vent openings between the specimen tube mouth and the bottom of the filter column to facilitate discharge of liquid into the specimen tube.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a perspective view of a filtration unit of this invention fitted to the mouth of a specimen tube;

FIG. 2 is a cross-sectional view on the line 2-2 of FIG. I, in the direction of the arrows; and

FIG. 3 illustrates the manner of insertion of filter paper into the filter column.

DETAILED DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENT As required, a detailed illustrative embodiment of the invention is disclosed herein. However, it is to be understood that this embodiment merely exemplifies the invention which may take many different forms that are radically different from the specific illustrative embodiment disclosed. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims defining the scope of the invention.

Referring to FIGS. 1 and 2, the filtration unit 10 includes a filter column 12 which is formed integral with a cap 14 at its bottom end for slide-fitting over the mouth of a sample tube 16. The filter column 12 is made of polyethylene or the like material and it is extruded integral with the cap 14. The filter column 12 is of elongate cylindrical construction so that its vertical dimension is at least as great as its longest horizontal dimension. the cylindrical form being particularly suitable. 1

The filter column 12 has an open top end 18 and abottom end 20 formed with flat marginal portions integrally of the column and terminating in a downwardly depending discharge tip 22 through which filtrate can flow by gravity. The cap 14 is cylindrically formed as a continuation of the filter column bottom 20 and extends downwardly somewhat beyond the end of the discharge tip 22. A plurality of vent openings 24 are defined by the cap 14 below the filter column bottom 20, for purposes hereinafter described.

The specimen tube 16 does not fonn a part of this invention except insofar as the filtration unit 10 is usable therewith. The specimen tube 16 is typical of such tubes utilized in automatic blood analysis equipment, and is formed with an exterior annular ridge 26 spaced from the mouth 28 of the specimen tube whereby it may be supported by a rack having holes sized for engagement with the ridges 26 of a plurality of such tubes 16 (or the rack may engage the tube 16 at an overhang 27). The top portion of the specimen tube 16 defining the mouth 28 is cylindrical and matingly engages the cylindrical cap 14.

Filter material in the form of cup-shaped filter paper 30 is disposed in the filter column 12 so that the flat, bottom portions thereof are flush against the internal fiat marginal portions 20 of the bottom of the filter column. The manner in which the filter paper 30 is formed cup-shaped and disposed within the filter column 12 is illustrated in FIG. 3. A small disc of filter paper 30, somewhat wider in diameter that the open top end 18 of the filter column 12, is disposed atop the column 12 and a glass rod 32, somewhat narrower than the inside diameter of the filter column 12, is pushed against the paper 30 until it is forced to the bottom 20 of the filter column, as indicated by the dashed line 30. The glass rod 32 is withdrawn, leaving the filter paper 30 having a cup-shaped form. By such means, filtering material is provided within the filter column 12 having only minor extent along the vertical dimension of the filter column and yet which effectively filters the specimen.

With respect to the specific dimensions, the specimen tube 16 typically utilized herein has a mouth 28 with an outer diameter of 1.4 centimeters. The inner diameter of the cap 14 is thus provided as 1.4 centimeters with a material thickness of 0.1 centimeter. The cap 14 is 1.0 centimeter deep and the filter column 12 is 5.0 centimeters long and has an inner diameter of 1.0 centimeter. The discharge tip 22 extends 0.7 centimeters from the bottom 20 of the filter bottom 12 and defines a filter hole 34 having a diameter of 0.2 centimeter. The filter paper 30 is 1.4 centimeters in diameter when fiat prior to being pressed to cup shape.

The top of the annular ridge 26 is spaced about 0.3 centimeter from the mouth 28 of the specimen tube 16. When assembled, the bottom edge 36 of the cap 14 slide-fits over the specimen tube mouth 28 and abuts the annular ridge 26. As aforenoted, the cap has a depth of about 1.0 centimeter with the result that the bottom 20 of the filter column 12 is spaced about 0.7 centimeter vertically from the specimen tube mouth 28.

discharge of filtrate.

in use, the plurality of specimen tubes 16 are assembled with filter columns 12 thereon as shown in FIG. 1 and placed in a tray which is utilized for automatic blood analysis and which is provided with'openings through which the specimen tubes are disposed and supported on the tray by means of the annular ridges 26. The specimen tubes 16 are labeled in correspondence with blood sample tube into the appropriate filter column 12 and is allowed to filter through the filter cup 30 into the specimen tube 16. During such gravity filtration, the tray containing the specimen tubes 16 can be carried about as desired without fear of misalignment, since the specimen tubes 16 carry their own filter columns 12. After the blood has completely filtered through into the specimen tubes 16, the filtration unit can be discarded.

It may be further noted that various analytical tests were conducted on blood samples which were filtered utilizing the foregoing filtration unit 10 and compared with the same blood unfiltered. After conducting many such comparisons, it was determined that no significant change in biochemical-composition was effected as a result of filtration by the method described herein.

lclaim:

l. A disposable filtration unit, comprising:

a one-piece hollow body formed with a lower end wall for supporting filter material internally of said body, said wall for supporting filter material internally of said body, said end wall formed with at least one liquid discharge opening and formed externally of said body with a dependent cap, said body having a sidewall defining a filtration column, for containing liquid to be filtered in direct con- .tact with said sidewall, and having an internal vertical dimension from said end wall at least as great as the longest horizontal dimension of said body;

filter material on said end wall comprising flat sheet portions directly supported flush on said end wall; and

' at least one opening defined through said cap wall.

2. The invention according to claim 1 in which said end wall is formed with a epending discharge tip defining said liquid discharge opening.

3. The invention according to claim 1 including a specimen tube having a cylindrical top portion defining a mouth therefor, said cap being defined by a cylindrical wall to friction fit the mouth of said specimen tube.

4. The invention according to claim 1 in which said end wall is formed with a depending discharge tip defining said liquid discharge opening and spaced axially centrally of said cap.

5. The invention according to claim 1 including a specimen tube having a cylindrical top portion defining a mouth therefor and an exterior annular ridge spaced from its mouth, said cap being formed to engage said annular ridge to thereby space said end wall from said mouth.

6. The invention according to claim 1 in which said filtration column is in the form of an elongate cylinder.

7. A disposable filtration unit comprising:

a one-piece hollow body formed with a lower end wall for supporting filter material internally of said body, the filter supporting surface of said end wall being substantially free from vertical protuberance, said end wall formed with at least one liquid discharge opening and formed externally of said body with a dependent cap, said body having a sidewall defining a filtration column, for containing liquid to be filtered in direct contact with said sidewall, and having an internal vertical dimension from said end wall at least as great as the longest internal horizontal dimension of said body;

filter material on said end wall in direct intimate contact with the filter supporting surface of said end wall;

at least one o ning defined through said cap wall. 8. The mven on according to claim 7 In which said filter material comprises filter paper having only minor extent along UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,608 736 Dated September 28, 1971 lnventofls) Johnson N. S Wong It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 3, line 12, cancel "tube" and insert tubes containing the individual patient's blood. Each blood specimen is then poured from the blood sample tube lines 30 and 31, cancel "said wall for supporting filter material internally of said body, Column 4, line 3, "epending" should read depending Signed and sealed this 10th day of October 1972.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents ORM 304050 10459) USCOMM-DC we're-Pen ".5v GOVERNMENT PRINYING OFFICE Qi O5$-33, 

1. A disposable filtration unit, comprising: a one-piece hollow body formed with a lower end wall for supporting filter material internally of said body, said wall for supporting filter material internally of said body, said end wall formed with at least one liquid discharge opening and formed externally of said body with a dependent cap, said body having a sidewall defining a filtration column, for containing liquid to be filtered in direct contact with said sidewall, and having an internal vertical dimension from said end wall at least as great as the longest horizontal dimension of said body; filter material on said end wall comprising flat sheet portions directly supported flush on said end wall; and at least one opening defined through said cap wall.
 2. The invention according to claim 1 in which said end wall is formed with a epending discharge tip defining said liquid discharge opening.
 3. The invention according to claim 1 including a specimen tube having a cylindrical top portion defining a mouth therefor, said cap being defined by a cylindrical wall to friction fit the mouth of said specimen tube.
 4. The invention according to claim 1 in which said end wall is formed with a depending discharge tip defining said liquid discharge opening and spaced axially centrally of said cap.
 5. The invention according to claim 1 including a specimen tube having a cylindrical top portion defining a mouth therefor and an exterior annular ridge spaced from its mouth, said cap being formed to engage said annular ridge to thereby space said end wall from said mouth.
 6. The invention according to claim 1 in which said filtration column is in the form of an elongate cylinder.
 7. A disposable filtration unit comprising: a one-piece hollow body formed with a lower end wall for supporting filter material internally of said body, the filter supporting surface of said end wall being substantially free from vertical protuberance, said end wall formed with at least one liquid discharge opening and formed externally of said body with a dependent cap, said body having a sidewall defining a filtration column, for containing liquid to be filtered in direct contact with said sidewall, and having an internal vertical dimension from said end wall at least as great as the longest internal horizontal dimension of said body; filter material on said end wall in direct intimate contact with the filter supporting surface of said end wall; at least one opening defined through said cap wall.
 8. The invention according to claim 7 in which said filter material comprises filter paper having only minor extent along said vertical dimension.
 9. The invention according to calim 7 in which said filter material comprises flat sheet portions directly supported flush on said end wall. 